The sodium content of portland cement is routinely determined by flame photometry. Some flame photometers were found consistently to indicate sodium contents of less than zero for certain cements.In addition, different brands of flame photometers almost never gave identical results for any cement.A study of the method showed that flame photometers having wide effective band widths gave low, often negative results, because of the inhibiting effect of silica on the emission of calcium oxide in the region of the sodium line. Increased accuracy was obtained by using an auxiliary multilayer interference filter to narrow the effective band width of the instrument or by removing the silica from the cement prior to the determination of the sodium.Both techniques together converted the current routine procedure into one which gave results substantially identical with those obtained by the gravimetric J. Lawrence Smith method, when using the Barclay, the Beckman DU, or the Perkin-Elmer flame photometer.

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Manganese is a minor constituent of portland cement. Its removal during analysis is frequently required in order to determine the true calcium and magnesium oxide values. Present federal and ASTM specification methods call for removal by bromine in ammoniacal solution, but do not always give consistent or complete removal of the manganese.A method based on oxidation by potassium permanganate in ammoniacal solution was suggested to ASTM Committee C-l and tried in several laboratories.This paper describes modifications of the originally suggested method which were found necessary in order to obtain satisfactory results. The permanganate method described gives better removal than the bromine procedure. No manganese could be detected in calcium precipitates and not over 0.003% MmO; in magnesium precipitates following such removal. The method is shown not to affect results for calcium and magnesium oxides when used in analysis of a high-manganese cement and NBS standard sample IA, argillaceous limestone.

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